Systems and methods for purification of fats, oils, and grease from wastewater

ABSTRACT

Embodiments of the present disclosure provide a system for purifying fats, oils, and grease from wastewater. The system may include a trash pump configured to pump the wastewater into the system, a grinder pump positioned downstream of the trash pump and configured to grind materials in the wastewater to form a process mixture, a plurality of heat exchangers positioned downstream of the grinder pump and configured to heat the process mixture, a shaker tray positioned downstream of the grinder pump and configured to remove solids from the process mixture, a decanter positioned downstream of the shaker tray and configured to remove solids from the process mixture, and a centrifuge positioned downstream of the decanter and configured to remove liquids and solids from the process mixture to form purified FOG.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.15/725,548, filed Oct. 5, 2017, which claims priority to U.S.Provisional Patent Application Ser. No. 62/404,897 filed on Oct. 6,2016, the entire contents of which are hereby incorporated by reference.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to wastewater treatment andmore particularly to systems and methods for purification of fats, oils,and grease from wastewater for subsequent use in biodiesel production.

BACKGROUND OF THE DISCLOSURE

A growing interest in biodiesel as a substitute for petroleum diesel hasled researchers to explore the use of various renewable sources as afeedstock for biodiesel production. Of particular interest is the optionof using fats, oils, and grease (FOG) present in wastewater as afeedstock alternative to virgin oil, waste vegetable oil, and otherpossible sources. In view of recent advances in economically convertingFOG into biodiesel and the continuous supply of wastewater produced inmodern society, the potential use of FOG extracted from wastewater forbiodiesel production is highly desirable. However, past efforts inpurifying FOG from wastewater have revealed significant problems inefficiently and effectively removing water and solid contaminants toproduce FOG that is suitable for conversion into biodiesel.Additionally, the equipment and processing costs associated with FOGrecovery from wastewater generally has been viewed as barrier toeconomically purifying FOG at wastewater treatment plants.

Accordingly, there remains a need for improved systems and methods forefficiently and effectively purifying FOG from wastewater at wastewatertreatment plants to provide FOG that is suitable for biodieselproduction.

SUMMARY OF THE DISCLOSURE

Various embodiments described herein provide systems and methods forpurification of fats, oils, and grease from wastewater for subsequentuse as a feedstock for biodiesel production. According to one aspect, asystem for purifying fats, oils, and grease (FOG) from wastewater isprovided. In one embodiment, the system may include a trash pump, agrinder pump, a plurality of heat exchangers, a shaker tray, a decanter,and a centrifuge. The trash pump may be configured to pump thewastewater into the system. The grinder pump may be positioneddownstream of the trash pump and configured to grind materials in thewastewater to form a process mixture. The heat exchangers may bepositioned downstream of the grinder pump and configured to heat theprocess mixture. The shaker tray may be positioned downstream of thegrinder pump and configured to remove solids from the process mixture.The decanter may be positioned downstream of the shaker tray andconfigured to remove solids from the process mixture. The centrifugepositioned downstream of the decanter and configured to remove liquidsand solids from the process mixture to form purified FOG.

In certain embodiments, the trash pump may be an auger style pump. Incertain embodiments, the trash pump may be supported by one or morefloats, such that the trash pump floats along a top of the wastewatercontained within a wastewater reservoir. In certain embodiments, thegrinder pump may be configured to grind the materials in the wastewaterto a maximum dimension of 0.25 inch or less. In certain embodiments, theplurality of heat exchangers may include a first heat exchangerpositioned downstream of the grinder pump and upstream of the shakertray, a second heat exchanger positioned downstream of the shaker trayand upstream of the decanter, a third heat exchanger positioneddownstream of the decanter and upstream of the centrifuge, and a fourthheat exchanger positioned downstream of the centrifuge. In certainembodiments, each of the heat exchangers may be configured to heat theprocess mixture to a temperature of between 185° F. and 200° F. Incertain embodiments, the system also may include a hot fluid boilerconfigured to supply a heating fluid to each of the heat exchangers forheating the process mixture. In certain embodiments, the hot fluidboiler may be a hot oil boiler, and the heating fluid may be hot oil.

In certain embodiments, the shaker tray may be configured to removesolids having a maximum dimension greater than 0.035 inch from theprocess mixture. In certain embodiments, the decanter may be configuredto remove solids from the process mixture such that the remainingprocess mixture contains less than 1% solids. In certain embodiments,the decanter may be a horizontal decanter. In certain embodiments, thecentrifuge may be configured to remove liquids and solids from theprocess mixture to form the purified FOG containing less than 2% waterand less than 0.1% solids. In certain embodiments, the centrifuge may bea vertical stack centrifuge. In certain embodiments, the system also mayinclude an auger in fluid communication with each of the shaker tray,the decanter, and the centrifuge, and the auger may be configured todeliver the removed solids and liquids to a waste reservoir. In certainembodiments, the system also may include a vent in fluid communicationwith each of the shaker tray, the decanter, and the centrifuge, and thevent may be configured to controllably release gases produced duringoperation of the shaker tray, the decanter, and the centrifuge.

In certain embodiments, the system also may include a controlleroperable to monitor a plurality of operating parameters of the system,and the controller may be in operable communication with a plurality ofsensors configured to indicate the operating parameters. In certainembodiments, the plurality of sensors may include a plurality oftemperature sensors configured to indicate the temperature of theprocess mixture at a plurality of points along the system, and aplurality of flow rate sensors configured to indicate the flow rate ofthe process mixture at a plurality of points along the system. Incertain embodiments, the controller may be in operable communicationwith each of the pumps, the heat exchangers, the shaker tray, thedecanter, and the centrifuge, and the controller may be operable tocontrol operation of the pumps, the heat exchangers, the shaker tray,the decanter, and the centrifuge based at least in part on the operatingparameters monitored by the controller. In certain embodiments, thesystem also may include a memory in operable communication with thecontroller and configured to store data corresponding to the operatingparameters monitored and controlled by the controller. In certainembodiments, the controller may be operable to compare current operatingparameters to the data stored by the memory and to selectively adjustone or more of the operating parameters to optimize a composition of thepurified FOG.

According to another aspect, a method for purifying fats, oils, andgrease (FOG) from wastewater is provided. In one embodiment, the methodmay include: pumping the wastewater into a system via a trash pump;grinding materials in the wastewater via a grinder pump to form aprocess mixture; heating the process mixture via a first heat exchanger;removing solids from the process mixture via a shaker tray; reheatingthe process mixture via a second heat exchanger; removing solids fromthe process mixture via a decanter; reheating the process mixture via athird heat exchanger; and removing liquids and solids from the processmixture via a centrifuge to form purified FOG.

In certain embodiments, the trash pump may be an auger style pump. Incertain embodiments, the method also may include allowing the trash pumpto float along a top of the wastewater contained within a wastewaterreservoir. In certain embodiments, grinding the materials in thewastewater via the grinder pump may include grinding the materials inthe wastewater to a maximum dimension of 0.25 inch or less. In certainembodiments, the first heat exchanger may heat the process mixture to atemperature of between 185° F. and 200° F., and the second heatexchanger and the third heat exchanger each may reheat the processmixture to a temperature of between 185° F. and 200° F. In certainembodiments, the method also may include reheating the purified FOG viaa fourth heat exchanger. In certain embodiments, removing the solidsfrom the process mixture via the shaker tray may include removing solidshaving a maximum dimension greater than 0.035 inch from the processmixture. In certain embodiments, the decanter may be a horizontaldecanter. In certain embodiments, removing the solids from the processmixture via the decanter may include removing the solids from theprocess mixture such that the remaining process mixture contains lessthan 1% solids. In certain embodiments, the centrifuge may be a verticalstack centrifuge. In certain embodiments, removing the liquids and thesolids from the process mixture via the centrifuge to form purified FOGmay include removing the liquids and the solids from the process mixtureto form the purified FOG containing less than 2% water and less than0.1% solids. In certain embodiments, the method also may includedelivering the solids and liquids removed by the shaker tray, thedecanter, and the centrifuge to a waste reservoir via an auger. Incertain embodiments, the method also may include controllably releasinggases produced during operation of the shaker tray, the decanter, andthe centrifuge via a vent.

In certain embodiments, the method also may include monitoring aplurality of operating parameters of the system via a controller inoperable communication with a plurality of sensors configured toindicate the operating parameters. In certain embodiments, monitoringthe operating parameters of the system may include monitoring thetemperature of the process mixture at a plurality of points along thesystem, and monitoring the flow rate of the process mixture at aplurality of points along the system. In certain embodiments, the methodalso may include controlling, via the controller, operation of thepumps, the heat exchangers, the shaker tray, the decanter, and thecentrifuge based at least in part on the operating parameters monitoredby the controller. In certain embodiments, the method also may includestoring, via a memory, data corresponding to the operating parametersmonitored and controlled by the controller. In certain embodiments, themethod also may include comparing, via the controller, current operatingparameters to the data stored by the memory and selectively adjustingone or more of the operating parameters to optimize a composition of thepurified FOG.

These and other aspects and embodiments of the present disclosure willbe apparent or will become apparent to one of ordinary skill in the artupon review of the following detailed description when taken inconjunction with the several drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In describing the various embodiments of the present disclosure,reference is made to the accompanying drawings, which are notnecessarily drawn to scale, and wherein:

FIG. 1A is a schematic diagram of a system for purification of fats,oils, and grease from wastewater.

FIG. 1B is a schematic diagram of system for purification of fats, oils,and grease from wastewater, including a mobile platform for transportingthe system.

FIG. 2 is a flow chart of a method for purification of fats, oils, andgrease from wastewater.

DETAILED DESCRIPTION OF THE DISCLOSURE

Various embodiments of the present disclosure provide improved systemsand methods for purification of fats, oils, and grease (FOG) fromwastewater for subsequent use as a feedstock for biodiesel production.Such systems and methods may address one or more of the above-describedproblems experienced with existing technology for FOG recovery fromwastewater at wastewater treatment plants.

Embodiments of the present disclosure are described herein below withreference to the accompanying drawings, in which some, but not all,embodiments are shown. Indeed, the systems and methods disclosed may beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure is thorough and complete and fullyconveys the scope of the systems and methods to those skilled in theart. Like reference numbers refer to like elements throughout. Thesingular forms “a,” “an,” and “the” can refer to plural instances unlessthe context clearly dictates otherwise or unless explicitly stated.

Referring now to the drawings, FIGS. 1A and 1B illustrate a FOGpurification system 100 (which also may be referred to as a “FOGharvester” or simply a “system”) according to one or more embodiments ofthe disclosure. As described in detail below, the FOG purificationsystem 100 may be used at a wastewater treatment plant to extract fats,oils, and grease (FOG) from wastewater. In contrast to existingtechnology, the FOG purification system 100 advantageously may providean efficient and effective means for removing water and solidcontaminants to produce FOG that is suitable for use as a feedstock forbiodiesel production. In this manner, use of the FOG purification system100 may take advantage of the continuous supply of wastewater, removeFOG that otherwise would be disposed of as environmental waste, andallow the purified FOG to be put to valuable use. In certainembodiments, the FOG purification system 100 may be provided as a mobilesystem, such that the system 100 may be transported to and operated at awastewater treatment plant when desired and then removed. In otherembodiments, the FOG purification system 100 may be provided as a fixedsystem, such that the system 100 is installed at a wastewater treatmentplant and operated continuously or at regular intervals.

The FOG purification system 100 may include a number of componentsarranged and configured such that wastewater WW input into the system100 is separated into purified FOG PF and waste W consisting of waterand solid materials removed from the wastewater WW. In certainembodiments, the purified FOG PF produced by the system 100 may be atleast 98% free of water and at least 99.9% free of solids. In otherwords, the purified FOG PF may contain less than 2% water and less than0.01% solids. In this manner, the purified FOG PF may be suitable foruse as a feedstock for the production of biodiesel. The schematicillustration of the FOG purification system 100 in FIGS. 1A and 1B showsvarious flows between the components of the system 100. It will beappreciated that the components may be in fluid communication with oneanother via suitable lines, pipes, or tubes, such that the various flowsare directed from one component to another component as shown. As usedherein, the term “process mixture” refers to the mixture of materialspassing through the FOG purification system 100 as the wastewater WW isseparated into purified FOG PF and waste W. It will be appreciated thatthe composition of the process mixture changes as the components of thesystem 100 remove water and solid materials to produce purified FOG PF.

As shown, the FOG purification system 100 may include a trash pump 104configured to pump the wastewater WW into the system 100. In certainembodiments, the trash pump 104 may be an auger style pump, althoughother types of pumps may be used for the trash pump 104. As shown, thetrash pump 104 may be supported by one or more floats 106, such aspontoons. In this manner, the trash pump 104 may float along the top ofthe wastewater WW contained within a wastewater reservoir WWR at awastewater treatment plant, with the inlet of the trash pump 104submerged in the wastewater WW. It will be appreciated that thewastewater WW may include liquids (e.g., water), semi-liquids (e.g.,FOG), and various solids (e.g., trash and other debris) that may makeits way into the wastewater reservoir WWR. The trash pump 104 may bespecifically configured to pump semi-solids, such as FOG, yet capable ofpumping any solids that enter the inlet of the trash pump 104. Inoperation, the trash pump 104, generally may receive liquid and floatingsolids (i.e., solids having a specific gravity less than the liquid),while heavier solids settle at the bottom of the wastewater reservoirWWR. Ultimately, the trash pump 104 pumps the wastewater WW out of thewastewater reservoir WWR and to a grinder pump 108 of the system 100.

The grinder pump 108 may be configured to grind all of the materials inthe wastewater WW and to pump the resulting process mixture downstreamfor further processing. In particular, the grinder pump 108 may beconfigured to grind all of the solid materials that the trash pump 104is able to deliver to the grinder pump 108. In certain embodiments, thegrinder pump 108 may be configured to grind all materials in thewastewater WW to a maximum dimension of 0.25 inch or less. In thismanner, the resulting process mixture leaving the grinder pump 108 mayflow more easily through downstream components of the system 100. Incertain embodiments, the grinder pump 108 may pump the process mixtureat a flow rate of between 20 gallons per minute and 40 gallons perminute, between 25 gallons per minute and 35 gallons per minute, orabout 30 gallons per minute. As shown, the grinder pump 108 may pump theprocess mixture to a first heat exchanger 112 of the system 100.

The first heat exchanger 112, which may be a large bore heat exchanger,may be configured to heat the process mixture such that the processmixture may flow more easily through downstream components of the system100. In particular, the heating of the process mixture may inhibitbuildup or clogging of semi-liquids, such as FOG, within the system 100.In certain embodiments, the first heat exchanger 112 may heat theprocess mixture to a temperature of between 185° F. and 200° F., orabout 185° F. As shown, the first heat exchanger 112 may be in fluidcommunication with a hot fluid boiler 114 which may supply a continuousflow of a heating fluid for heating the process mixture within the firstheat exchanger 112. In certain embodiments, the hot fluid boiler 114 maybe a hot oil boiler and the heating fluid may be hot oil. In certainembodiments, the heating fluid may be supplied to the first heatexchanger 112 at a temperature of between 240° F. and 260° F., or about250° F. In other embodiments, the heating fluid may be supplied to thefirst heat exchanger 112 at other temperatures sufficient to adequatelyheat the process mixture. As shown, after exiting the first heatexchanger 112, the cooled heating fluid may be returned to the hot fluidboiler 114 for reheating and reuse within the system 100. The heatedprocess mixture (at a temperature of between 185° F. and 200° F.) may bedelivered from the first heat exchanger 112 to one or more shaker trays116.

The shaker trays 116 may be configured to remove any material having amaximum dimension greater than 0.035 inch from the process mixture.Although the illustrated embodiment of the FOG purification system 100includes two shaker trays 116, the system 100 may include any number ofshaker trays 116 (one, three, or more). In embodiments of the system 100which include more than one shaker tray 116, a valve 118 may bepositioned between the first heat exchanger 112 and the shaker trays116, as shown, to control delivery of the process mixture to the shakertrays 116. For example, the valve 118 may be a three-way valve forcontrolling delivery of the process mixture to the two shaker trays 116.In certain embodiments, only one of the shaker trays 116 may be operatedat a time, such that the valve 118 directs the process mixture to one ofthe shaker trays 116, while the other shaker tray 116 may be turned off.In other embodiments, both of the shaker trays 116 may be operatedsimultaneously. As shown, the shaker trays 116 may be in fluidcommunication with a vent 122 of the system 100 via one or more lines,pipes, or tubes. In this manner, gases produced during operation of theshaker trays 116 may be collected and directed to the vent 122 forcontrolled release from the system 100. As shown, the material removedby the shaker trays 116 (i.e., material having a maximum dimensiongreater than 0.035 inch) may be directed to an auger 124, which maydeliver the waste W to a waste reservoir WR of the wastewater treatmentplant for landfill collection and/or further treatment. The remainingprocess mixture, consisting of liquids, semi-liquids, and small solids,may be directed from the shaker trays 116 to a centrifugal pump 126.

The centrifugal pump 126 may be configured to pump the remaining processmixture to a second heat exchanger 132 of the system 100. The secondheat exchanger 132, which may be a large bore heat exchanger, may beconfigured to reheat the process mixture such that the process mixturemay continue to flow more easily through downstream components of thesystem 100. In certain embodiments, the second heat exchanger 132 mayheat the process mixture to a temperature of between 185° F. and 200°F., or about 200° F. As shown, the second heat exchanger 132 may be influid communication with the hot fluid boiler 114 which may supply acontinuous flow of the heating fluid for heating the process mixturewithin the second heat exchanger 132. In certain embodiments, theheating fluid may be supplied to the second heat exchanger 132 at atemperature of between 240° F. and 260° F., or about 250° F. In otherembodiments, the heating fluid may be supplied to the second heatexchanger 132 at other temperatures sufficient to adequately heat theprocess mixture to inhibit buildup or clogging of semi-liquids, such asFOG. As shown, after exiting the second heat exchanger 132, the cooledheating fluid may be returned to the hot fluid boiler 114 for reheatingand reuse within the system 100. The reheated process mixture (at atemperature of between 185° F. and 200° F.) may be delivered from thesecond heat exchanger 132 to a decanter 134.

The decanter 134 may be configured to remove substantially all of theremaining solids from the process mixture. In certain embodiments, thedecanter 134 may be a horizontal decanter, as shown. In certainembodiments, the decanter 134 may be configured to remove at least 99%of all solids from the process mixture. In other words, the processmixture output by the decanter 134 may contain less than 1% solids. Asshown, the decanter 134 may be in fluid communication with the vent 122via one or more lines, pipes, or tubes. In this manner, gases producedduring operation of the decanter 134 may be collected and directed tothe vent 122 for controlled release from the system 100. As shown, thematerial removed by the decanter 134 (i.e., a majority of the solids)may be directed to the auger 124, which may deliver the waste W to thewaste reservoir WR for landfill collection and/or further treatment. Theremaining process mixture, consisting of liquids, semi-liquids, andlimited amount of solids, may be directed from the decanter 134 to amechanical pump 136.

The mechanical pump 136 may be configured to pump the remaining processmixture to a third heat exchanger 142 of the system 100. The third heatexchanger 142, which may be a large bore heat exchanger, may beconfigured to reheat the process mixture such that the process mixturemay continue to flow more easily through downstream components of thesystem 100. In certain embodiments, the third heat exchanger 142 mayheat the process mixture to a temperature of between 185° F. and 200°F., or about 200° F. As shown, the third heat exchanger 142 may be influid communication with the hot fluid boiler 114 which may supply acontinuous flow of the heating fluid for heating the process mixturewithin the third heat exchanger 142. In certain embodiments, the heatingfluid may be supplied to the third heat exchanger 142 at a temperatureof between 240° F. and 260° F., or about 250° F. In other embodiments,the heating fluid may be supplied to the third heat exchanger 142 atother temperatures sufficient to adequately heat the process mixture toinhibit buildup or clogging of semi-liquids, such as FOG. As shown,after exiting the third heat exchanger 142, the cooled heating fluid maybe returned to the hot fluid boiler 114 for reheating and reuse withinthe system 100. The reheated process mixture (at a temperature ofbetween 185° F. and 200° F.) may be delivered from the third heatexchanger 142 to a centrifuge 144.

The centrifuge 144 may be configured to remove substantially all of theremaining liquids and solids from the process mixture. In certainembodiments, the centrifuge 144 may be a vertical stack centrifuge, asshown. In certain embodiments, the centrifuge 144 may be configured toremove at least 98% of all water and at least 99.9% of all solids fromthe process mixture. In other words, the process mixture output by thecentrifuge 144 may contain less than 2% water and less than 0.1% solids.As shown, the centrifuge 144 may be in fluid communication with the vent122 via one or more lines, pipes, or tubes. In this manner, gasesproduced during operation of the centrifuge 144 may be collected anddirected to the vent 122 for controlled release from the system 100. Asshown, the material removed by the centrifuge 144 (i.e., a majority ofthe water and the solids) may be directed to the auger 124, which maydeliver the waste W to the waste reservoir WR for landfill collectionand/or further treatment. The remaining process mixture, consisting ofprimarily of semi-liquids and very limited amounts of liquids andsolids, may be directed from the centrifuge 144 to a mechanical pump146. In other words, the remaining process mixture may be purified FOGPF which is at least 98% free of water and at least 99.9% free ofsolids.

The mechanical pump 146 may be configured to pump the purified FOG PF toa fourth heat exchanger 152 of the system 100. The fourth heat exchanger152, which may be a large bore heat exchanger, may be configured toreheat the purified FOG PF such that the purified FOG PF may continue toflow more easily to downstream components of the system 100. In certainembodiments, the fourth heat exchanger 152 may heat the purified FOG PFto a temperature of between 185° F. and 200° F., or about 200° F. Asshown, the fourth heat exchanger 152 may be in fluid communication withthe hot fluid boiler 114 which may supply a continuous flow of theheating fluid for heating the purified FOG PF within the fourth heatexchanger 152. In certain embodiments, the heating fluid may be suppliedto the fourth heat exchanger 152 at a temperature of between 240° F. and260° F., or about 250° F. In other embodiments, the heating fluid may besupplied to the fourth heat exchanger 152 at other temperaturessufficient to adequately heat the purified FOG PF to inhibit buildup orclogging thereof. As shown, after exiting the fourth heat exchanger 152,the cooled heating fluid may be returned to the hot fluid boiler 114 forreheating and reuse within the system 100. The purified FOG PF (at atemperature of between 185° F. and 200° F.) may be delivered from thefourth heat exchanger 152 to a storage vessel 154. As shown, the storagevessel 154 may be in fluid communication with the vent 122 via one ormore lines, pipes, or tubes. In this manner, gases produced as thepurified FOG PF settles in the storage vessel 154 may be collected anddirected to the vent 122 for controlled release from the system 100. Incertain embodiments, the storage vessel 154 may have a caustic scrubber,such as sodium hydroxide, therein to control odors produced by thepurified FOG PF. The purified FOG PF collected in the storage vessel 154ultimately may be used as a feedstock for biodiesel production.

As shown, the FOG purification system 100 may include a controller 162,which may be a programmable logic controller (PLC). The controller 162may be operable to monitor various operating parameters of the system100 and to control operation of the above-described components of thesystem 100. In certain embodiments, the controller 162 may be inoperable communication with sensors positioned along the various lines,pipes, or tubes extending between the system 100 components. The sensorsmay include temperature sensors configured to indicate the temperatureof the process mixture at certain points along the system 100, forexample, immediately upstream and downstream of each of the heatexchangers 112, 132, 142, 152. Additional temperature sensors may beused to indicate the temperature of the heating fluid at certain pointsalong the system 100, for example, immediately upstream and downstreamof each of the heat exchangers 112, 132, 142, 152 and immediatelyupstream and downstream of the hot fluid boiler 114. The sensors alsomay include flow rate sensors configured to indicate the flow rate ofthe process mixture at certain points along the system 100, for example,immediately upstream and downstream of each of the pumps 104, 108, 126,136, 146, immediately upstream and downstream of each of the heatexchangers 112, 132, 142, 152, and/or immediately upstream anddownstream of each of the shaker trays 116, the decanter 134, and thecentrifuge 144. Additional flow rate sensors may be used to indicate theflow rate of the heating fluid at certain points along the system 100,for example, immediately upstream and downstream of each of the heatexchangers 112, 132, 142, 152 and immediately upstream and downstream ofthe hot fluid boiler 114. The sensors further may include a volumetricsensor positioned on or within the storage vessel 154 and configured toindicate the volume of the purified FOG PF contained therein. Thesensors may include still other types of sensors to allow the controller162 to monitor other operating parameters of the system 100.

The controller 162 also may be operable to control operation of theabove-described components of the system 100. As shown, the controller162 may be in operable communication with each of the pumps 104, 108,126, 136, 146, the heat exchangers 112, 132, 142, 152, the shaker trays116, the valve 118, the vent 124, the decanter 134, the centrifuge 144,and the storage vessel 154. In certain embodiments, the controller 162may be operable to control (i.e., increase, decrease, or maintain) thespeeds of the pumps 104, 108, 126, 136, 146, thereby controlling theflow rate of the process mixture being output by each of the pumps 104,108, 126, 136, 146. For example, the controller 162 may be operable tocontrol the speeds of the pumps 104, 108, 126, 136, 146 based at leastin part on the flow rates indicated by the flow rate sensors and/or thetemperatures indicated by the temperature sensors. In certainembodiments, the controller 162 also may be operable to control thetemperature of the heating fluid being delivered to the heat exchangers112, 132, 142, 152, thereby controlling the temperature of the processmixture being output by each of the heat exchangers 112, 132, 142, 152.For example, the controller 162 may be operable to control thetemperature of the heating fluid being delivered to the heat exchangers112, 132, 142, 152 based at least in part on the flow rates indicated bythe flow rate sensors and/or the temperatures indicated by thetemperature sensors. In certain embodiments, the controller 162 furthermay be operable to control the speeds of the shaker trays 116, thedecanter 134, and the centrifuge 144, thereby controlling the rates atwhich the shaker trays 116 and the decanter 134 remove solids from theprocess mixture and at which the centrifuge 144 removes liquids andsolids from the process mixture. For example, the controller 162 may beoperable to control the speeds of the shaker trays 116, the decanter134, and the centrifuge 144 based at least in part on the flow ratesindicated by the flow rate sensors and/or the temperatures indicated bythe temperature sensors.

As shown, the FOG purification system 100 also may include a memory 164in operable communication with the controller 162. The memory 164 may beconfigured to store data corresponding to the various operatingparameters that are monitored and controlled by the controller 162(i.e., temperatures, flow rates, volumes, and speeds). In certainembodiments, the controller 162 may compare current (i.e., real-time)operating parameters to the data stored in the memory 164 andselectively adjust one or more of the operating parameters to optimizethe FOG purification process (i.e., to optimize the composition of thepurified FOG PF). In this manner, the controller 162 may ensure that theFOG purification system 100 operates in an efficient and effectivemanner to extract the FOG from the wastewater.

In certain embodiments, the above-described components of the FOGpurification system 100 may be mounted on a platform or a skid 170, asshown in FIG. 1B. In this manner, the entire system 100 may be easilytransported, for example via a tractor-trailer, to a wastewatertreatment plant for operation. The platform 170 may be positioned nearthe wastewater reservoir WWR, and the trash pump 104 and float 106 maybe moved into the reservoir WWR, while the remainder of the system 100remains fixedly mounted to the platform 170. In some embodiments, themobile platform 170 may be a trailer, container, or other suitablestructure for supporting and moving the other components of the system100 as a unit from one location to another location. Although theplatform 170 is shown as including a plurality of wheels 172, theplatform 170 may include alternative mechanisms for moving the system100 to different locations. In some embodiments, the platform 170 mayinclude an enclosure 174 containing the other components of the system100 therein. In other embodiments, the FOG purification system 100 maybe permanently installed at the wastewater treatment plant near thewastewater reservoir WWR.

FIG. 2 illustrates a method 200 for purifying fats, oils, and grease(FOG) from wastewater, according to one or more embodiments of thedisclosure. The method 200 may include, at step 202, pumping wastewaterfrom a wastewater reservoir. In certain embodiments, the wastewater maybe pumped from the wastewater reservoir via a trash pump, such as anauger style trash pump. At step 204, the method 200 may include grindingthe materials in the wastewater to form a process mixture. In certainembodiments, the materials in the wastewater may be ground via grinderpump to a maximum dimension of 0.25 inch or less. The method 200 alsomay include, at step 206, heating the process mixture to a temperatureof between 185° F. and 200° F., or about 185° F. In certain embodiments,the process mixture may be heated via a heat exchanger, such as a largebore heat exchanger.

At step 208, the method 200 may include removing materials having amaximum dimension greater than 0.035 inch from the process mixture. Incertain embodiments, such removal may be achieved via a shaker tray. Themethod 200 also may include, at step 210, reheating the remainingprocess mixture to a temperature of between 185° F. and 200° F., orabout 200° F. In certain embodiments, the remaining process mixture maybe reheated via a heat exchanger, such as a large bore heat exchanger.At step 212, the method 200 may include removing substantially all ofthe remaining solids from the process mixture such that the remainingprocess mixture contains less than 1% solids. In certain embodiments,such removal may be achieved via a decanter, such as a horizontaldecanter. The method 200 also may include, at step 214, reheating theremaining process mixture to a temperature of between 185° F. and 200°F., or about 200° F. In certain embodiments, the remaining processmixture may be reheated via a heat exchanger, such as a large bore heatexchanger.

At step 216, the method 200 may include removing substantially all ofthe remaining liquids and solids from the process mixture such that theremaining process mixture contains less than 2% water and less than 0.1%solids, thereby forming purified FOG. In certain embodiments, suchremoval may be achieved via a centrifuge, such as a vertical stackcentrifuge. The method 200 also may include, at step 218, reheating thepurified FOG to a temperature of between 185° F. and 200° F., or about200° F. In certain embodiments, the purified FOG may be reheated via aheat exchanger, such as a large bore heat exchanger. At step 220, themethod may include storing the purified FOG in a storage vessel forsubsequent use as a feedstock for biodiesel product.

The purified FOG prepared by the method 200 may be used as a feedstockfor biodiesel production according to various processes. As one example,the purified FOG may be used as a feedstock for the production of alkylesters, such as biodiesel according to the methods described inInternational Application No. PCT/US2015/031570 (InternationalPublication No. WO 2016/089443), the entire contents of which are herebyincorporated by reference. According to such methods, at least oneenzyme and alcohol may be added to the purified FOG to elicit an enzymecatalyzed reaction with the purified FOG, thereby forming reactedcontents which are used in a double distillation process to producebiodiesel.

Many modifications of the embodiments of the present disclosure willcome to mind to one skilled in the art to which the disclosure pertainsupon having the benefit of the teachings presented herein through theforegoing descriptions and the associated drawings. Therefore, it is tobe understood that the present invention is not to be limited to thespecific embodiments disclosed and that modifications and otherembodiments are intended to be included within the scope of the appendedclaims. Although specific terms are employed herein, they are used in ageneric and descriptive sense only and not for purposes of limitation.

What is claimed is:
 1. A method for purifying fats, oils, and grease(FOG) from wastewater, the method comprising: pumping the wastewaterinto a FOG purification system via a trash pump; grinding materials inthe wastewater via a grinder pump to form a process mixture; heating theprocess mixture via a first heat exchanger; removing solids from theprocess mixture via a shaker tray; reheating the process mixture via asecond heat exchanger; removing solids from the process mixture via adecanter; reheating the process mixture via a third heat exchanger; andremoving liquids and solids from the process mixture via a centrifuge toform purified FOG, wherein the FOG purification system comprises thetrash pump, the grinder pump, the first heat exchanger, the shaker tray,the second heat exchanger, the decanter, the third heat exchanger, andthe centrifuge.
 2. The method of claim 1, further comprising: allowingthe trash pump to float along the top of the wastewater contained in awastewater reservoir; delivering the solids and liquids removed by theshaker tray, the decanter, and the centrifuge to a waste reservoir viaan auger; and controllably releasing gases produced during operation ofthe shaker tray, the decanter, and the centrifuge via a vent.
 3. Themethod of claim 1, wherein grinding the materials in the wastewater viathe grinder pump comprises grinding the materials in the wastewater to amaximum dimension of 0.25 inch or less, wherein removing the solids fromthe process mixture via the shaker tray comprises removing solids havinga maximum dimension greater than 0.035 inch from the process mixture,wherein removing the solids from the process mixture via the decantercomprises removing the solids from the process mixture such that theremaining process mixture contains less than 1% solids, wherein removingthe liquids and the solids from the process mixture via the centrifugeto form purified FOG comprises removing the liquids and the solids fromthe process mixture to form the purified FOG containing less than 2%water and less than 0.1% solids.
 4. The method of claim 1, wherein thetrash pump is an auger style pump, wherein the decanter comprises ahorizontal decanter, and wherein the centrifuge comprises a verticalstack centrifuge.
 5. The method of claim 1, wherein the first heatexchanger heats the process mixture to a temperature of between 185° F.and 200° F., and wherein the second heat exchanger and the third heatexchanger each reheat the process mixture to a temperature of between185° F. and 200° F.
 6. The method of claim 1, further comprisingmonitoring a plurality of operating parameters of the FOG purificationsystem via a controller in operable communication with a plurality ofsensors configured to indicate the operating parameters, whereinmonitoring the operating parameters of the FOG purification systemcomprises monitoring the temperature of the process mixture at aplurality of points along the FOG purification system, and monitoringthe flow rate of the process mixture at a plurality of points along theFOG purification system.
 7. The method of claim 6, further comprising:controlling, via the controller, operation of the pumps, the heatexchangers, the shaker tray, the decanter, and the centrifuge based atleast in part on the operating parameters monitored by the controller;storing, via a memory, data corresponding to the operating parametersmonitored and controlled by the controller; and comparing, via thecontroller, current operating parameters to the data stored by thememory and selectively adjusting one or more of the operating parametersto optimize a composition of the purified FOG.